Loop structures for supporting diagnostic and therapeutic elements in contact with body tissue

ABSTRACT

A probe that facilitates the creation of circumferential lesions in body tissue. The probe includes a elongate body and a loop structure that supports electrodes or other operative elements against the body tissue.

BACKGROUND OF THE INVENTIONS

[0001] 1. Field of Inventions

[0002] The present invention relates generally to medical devices thatsupport one or more diagnostic or therapeutic elements in contact withbody tissue and, more particularly, to medical devices that support oneor more diagnostic or therapeutic elements in contact with bodilyorifices or the tissue surrounding such orifices.

[0003] 2. Description of the Related Art

[0004] There are many instances where diagnostic and therapeuticelements must be inserted into the body. One instance involves thetreatment of cardiac conditions such as atrial fibrillation and atrialflutter which lead to an unpleasant, irregular heart beat, calledarrhythmia.

[0005] Normal sinus rhythm of the heart begins with the sinoatrial node(or “SA node”) generating an electrical impulse. The impulse usuallypropagates uniformly across the right and left atria and the atrialseptum to the atrioventricular node (or “AV node”). This propagationcauses the atria to contract in an organized way to transport blood fromthe atria to the ventricles, and to provide timed stimulation of theventricles. The AV node regulates the propagation delay to theatrioventricular bundle (or “HIS” bundle). This coordination of theelectrical activity of the heart causes atrial systole duringventricular diastole. This, in turn, improves the mechanical function ofthe heart. Atrial fibrillation occurs when anatomical obstacles in theheart disrupt the normally uniform propagation of electrical impulses inthe atria. These anatomical obstacles (called “conduction blocks”) cancause the electrical impulse to degenerate into several circularwavelets that circulate about the obstacles. These wavelets, called“reentry circuits,” disrupt the normally uniform activation of the leftand right atria.

[0006] Because of a loss of atrioventricular synchrony, the people whosuffer from atrial fibrillation and flutter also suffer the consequencesof impaired hemodynamics and loss of cardiac efficiency. They are alsoat greater risk of stroke and other thromboembolic complications becauseof loss of effective contraction and atrial stasis.

[0007] One surgical method of treating atrial fibrillation byinterrupting pathways for reentry circuits is the so-called “mazeprocedure” which relies on a prescribed pattern of incisions toanatomically create a convoluted path, or maze, for electricalpropagation within the left and right atria. The incisions direct theelectrical impulse from the SA node along a specified route through allregions of both atria, causing uniform contraction required for normalatrial transport function. The incisions finally direct the impulse tothe AV node to activate the ventricles, restoring normalatrioventricular synchrony. The incisions are also carefully placed tointerrupt the conduction routes of the most common reentry circuits. Themaze procedure has been found very effective in curing atrialfibrillation. However, the maze procedure is technically difficult todo. It also requires open heart surgery and is very expensive.

[0008] Maze-like procedures have also been developed utilizing catheterswhich can form lesions on the endocardium (the lesions being 1 to 15 cmin length and of varying shape) to effectively create a maze forelectrical conduction in a predetermined path. The formation of theselesions by soft tissue coagulation (also referred to as “ablation”) canprovide the same therapeutic benefits that the complex incision patternsthat the surgical maze procedure presently provides, but withoutinvasive, open heart surgery.

[0009] Catheters used to create lesions typically include a relativelylong and relatively flexible body portion that has a soft tissuecoagulation electrode on its distal end and/or a series of spaced tissuecoagulation electrodes near the distal end. The portion of the catheterbody portion that is inserted into the patient is typically from 23 to55 inches in length and there may be another 8 to 15 inches, including ahandle, outside the patient. The length and flexibility of the catheterbody allow the catheter to be inserted into a main vein or artery(typically the femoral artery), directed into the interior of the heart,and then manipulated such that the coagulation electrode contacts thetissue that is to be ablated. Fluoroscopic imaging is used to providethe physician with a visual indication of the location of the catheter.

[0010] In some instances, the proximal end of the catheter body isconnected to a handle that includes steering controls. Exemplarycatheters of this type are disclosed in U.S. Pat. No. 5,582,609. Inother instances, the catheter body is inserted into the patient througha sheath and the distal portion of the catheter is bent into loop thatextends outwardly from the sheath. This may be accomplished by pivotablysecuring the distal end of the catheter to the distal end of the sheath,as is illustrated in co-pending U.S. application Ser. No. 08/769,856,filed Dec. 19, 1996, and entitled “Loop Structures for SupportingMultiple Electrode Elements.” The loop is formed as the catheter ispushed in the distal direction. The loop may also be formed by securinga pull wire to the distal end of the catheter that extends back throughthe sheath, as is illustrated in co-pending U.S. application Ser. No.08/960,902, filed Oct. 30, 1997, and entitled, “Catheter Distal AssemblyWith Pull Wires,” which is incorporated herein by reference. Loopcatheters are advantageous in that they tend to conform to differenttissue contours and geometries and provide intimate contact between thespaced tissue coagulation electrodes (or other diagnostic or therapeuticelements) and the tissue.

[0011] One lesion that has proven to be difficult to form withconventional devices is the circumferential lesion that is used toisolate the pulmonary vein and cure ectopic atrial fibrillation. Lesionsthat isolate the pulmonary vein may be formed within the pulmonary veinitself or in the tissue surrounding the pulmonary vein. Conventionalsteerable catheters and loop catheters have proven to be less thaneffective with respect to the formation of such circumferential lesions.Specifically, it is difficult to form an effective circumferentiallesion by forming a pattern of relatively small diameter lesions. Morerecently, inflatable balloon-like devices that can be expanded within oradjacent to the pulmonary vein have been introduced. Although theballoon-like devices are generally useful for creating circumferentiallesions, the inventors herein have determined that these devices havethe undesirable effect of occluding blood flow through the pulmonaryvein.

[0012] Accordingly, the inventors herein have determined that a needexists generally for structures that can be used to createcircumferential lesions within or around bodily orifices withoutoccluding fluid flow and, in the context of the treatment of atrialfibrillation, within or around the pulmonary vein without occludingblood flow.

SUMMARY OF THE INVENTION

[0013] Accordingly, the general object of the present inventions is toprovide a device that avoids, for practical purposes, the aforementionedproblems. In particular, one object of the present inventions is toprovide a device that can be used to create circumferential lesions inor around the pulmonary vein and other bodily orifices in a moreefficient manner than conventional apparatus. Another object of thepresent invention is to provide a device that can be used to createcircumferential lesions in or around the pulmonary vein and other bodilyorifices without occluding blood or other bodily fluid flow.

[0014] In order to accomplish some of these and other objectives, aprobe in accordance with one embodiment of a present invention includesan elongate body and a helical structure associated with the distalregion of the elongate body. In one preferred implementation, aplurality of spaced electrodes are carried by the helical structure.Such a probe provides a number of advantages over conventionalapparatus. For example, the helical structure can be readily positionedwith the body such that a ring of electrodes is brought into contactwith the tissue in or around the pulmonary or other bodily orifice. Thehelical structure also defines an opening that allows blood or otherbodily fluids to pass therethrough. As a result, the present probefacilitates the formation of a circumferential lesion without thedifficulties and occlusion of blood or other fluids that is associatedwith conventional apparatus.

[0015] In order to accomplish some of these and other objectives, aprobe in accordance with one embodiment of a present invention includesan elongate body, a loop structure associated with the distal region ofthe elongate body, and an anchor member associated with the distalregion of the elongate body and located distally of the loop structure.In one preferred implementation, a plurality of spaced electrodes arecarried by the loop structure. Such a probe provides a number ofadvantages over conventional apparatus. For example, the anchor membermay be positioned within a bodily orifice, such as the pulmonary vein,thereby centering the loop structure relative to the orifice. Thisallows a circumferential lesion to be created in or around the pulmonaryvein or other orifice without the aforementioned difficulties associatedwith conventional apparatus.

[0016] In order to accomplish some of these and other objectives, aprobe in accordance with one embodiment of a present invention includesan elongate body defining a curved portion having a pre-set curvatureand a control element defining a distal portion associated with thedistal region of the elongate body and extending outwardly therefrom andproximally to the proximal end of the elongate body. In one preferredimplementation, a plurality of spaced electrodes are carried by thedistal region of the elongate body. Such a probe provides a number ofadvantages over conventional apparatus. For example, the control elementmay be used to pull the distal region of the elongate body into a loopin conventional fashion. Unlike conventional apparatus, however, thepre-set curvature of the curved portion may be such that it orients theloop in such a manner that it can be easily positioned in or around thepulmonary vein or other bodily orifice so that a circumferential lesioncan be easily formed.

[0017] The above described and many other features and attendantadvantages of the present inventions will become apparent as theinventions become better understood by reference to the followingdetailed description when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Detailed description of preferred embodiments of the inventionswill be made with reference to the accompanying drawings.

[0019]FIG. 1 is a side view of a probe in a relaxed state in accordancewith a preferred embodiment of a present invention.

[0020]FIG. 2 is a section view taken along line 2-2 in FIG. 1.

[0021]FIG. 3 is a side view of the probe illustrated in FIG. 1 with thestylet extended.

[0022]FIG. 4 is a side view of the probe illustrated in FIG. 1 with thestylet retracted.

[0023]FIG. 5a is an end view of the probe illustrated in FIG. 4.

[0024]FIG. 5b is a section view taken along line 5 b-5 b in FIG. 5a.

[0025]FIG. 6 is a side view of the probe illustrated in FIG. 1 in anexpanded state.

[0026]FIG. 7 is an end view of the probe illustrated in FIG. 6.

[0027]FIG. 8 is a perspective, cutaway view of a probe handle inaccordance with a preferred embodiment of a present invention.

[0028]FIG. 9 is a perspective view of a portion of the probe handleillustrated in FIG. 8.

[0029]FIG. 10 is an exploded view of the portion of the probe handleillustrated in FIG. 9.

[0030]FIG. 11 is a partial section view taken along line 11-11 in FIG.9.

[0031]FIG. 12 is a partial section view of the knob and spoolarrangement in the probe handle illustrated in FIG. 8.

[0032]FIG. 13 is a perspective view of a probe handle in accordance witha preferred embodiment of a present invention.

[0033]FIG. 14 is an exploded view of the probe handle illustrated inFIG. 13.

[0034]FIG. 15 is a partial section view taken along line 15-15 in FIG.13.

[0035]FIG. 16 is a side view of a probe in accordance with a preferredembodiment of a present invention.

[0036]FIG. 16a is a side view of a probe in accordance with a preferredembodiment of a present invention.

[0037]FIG. 16b is a section view taken alone line 16 a-16 b in FIG. 16a.

[0038]FIG. 16c is a perspective view of the probe illustrated in FIG.16a in a helical orientation.

[0039]FIG. 17 is a plan view of a probe in accordance with a preferredembodiment of a present invention.

[0040]FIG. 18 is a section view of the distal portion of the probeillustrated in FIG. 17.

[0041]FIG. 19 is a side, partial section view showing the probeillustrated in FIG. 17 within a sheath.

[0042]FIG. 20 is a perspective view of the probe illustrated in FIG. 17with the loop reoriented.

[0043]FIG. 21 is a side view of the probe illustrated in FIG. 20.

[0044]FIG. 22 is a perspective view of a probe in accordance with apreferred embodiment of a present invention.

[0045]FIG. 23 is a side view of the probe illustrated in FIG. 22.

[0046]FIG. 24 is an end view of the probe illustrated in FIG. 22.

[0047]FIG. 25 is a side view of the probe illustrated in FIG. 22 beingused in combination with a sheath and a guidewire.

[0048]FIG. 26 is an end view of a probe similar to that illustrated inFIGS. 22-24 with a generally elliptical loop.

[0049]FIG. 27 is a side, partial section view showing a probe inaccordance with a preferred embodiment of a present invention.

[0050]FIG. 28 is a perspective view of the probe illustrated in FIG. 27with the loop reoriented.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] The following is a detailed description of the best presentlyknown modes of carrying out the inventions. This description is not tobe taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions.

[0052] The detailed description of the preferred embodiments isorganized as follows:

[0053] I. Introduction

[0054] II. Helical Loop Structures

[0055] III. Other Loop Structures

[0056] IV. Electrodes, Temperature Sensing and Power Control

[0057] The section titles and overall organization of the presentdetailed description are for the purpose of convenience only and are notintended to limit the present inventions.

[0058] I. Introduction

[0059] The present inventions may be used within body lumens, chambersor cavities for diagnostic or therapeutic purposes in those instanceswhere access to interior bodily regions is obtained through, forexample, the vascular system or alimentary canal and without complexinvasive surgical procedures. For example, the inventions herein haveapplication in the diagnosis and treatment of arrhythmia conditionswithin the heart. The inventions herein also have application in thediagnosis or treatment of ailments of the gastrointestinal tract,prostrate, brain, gall bladder, uterus, and other regions of the body.

[0060] With regard to the treatment of conditions within the heart, thepresent inventions are designed to produce intimate tissue contact withtarget substrates associated with various arrhythmias, namely atrialfibrillation, atrial flutter, and ventricular tachycardia. For example,the distal portion of a catheter in accordance with a present invention,which may include diagnostic and/or soft tissue coagulation electrodes,can be used to create lesions within or around the pulmonary vein totreat ectopic atrial fibrillation.

[0061] The structures are also adaptable for use with probes other thancatheter-based probes. For example, the structures disclosed herein maybe used in conjunction with hand held surgical devices (or “surgicalprobes”). The distal end of a surgical probe may be placed directly incontact with the targeted tissue area by a physician during a surgicalprocedure, such as open heart surgery. Here, access may be obtained byway of a thoracotomy, median sternotomy, or thoracostomy. Exemplarysurgical probes are disclosed in co-pending U.S. application Ser. No.09/072,872, filed May 5, 1998, and entitled “Surgical Methods andApparatus for Positioning a Diagnostic or Therapeutic Element Within theBody.”

[0062] Surgical probe devices in accordance with the present inventionspreferably include a handle, a relatively short shaft, and one of thedistal assemblies described hereafter in the catheter context.Preferably, the length of the shaft is about 4 inches to about 18inches. This is relatively short in comparison to the portion of acatheter body that is inserted into the patient (typically from 23 to 55inches in length) and the additional body portion that remains outsidethe patient. The shaft is also relatively stiff. In other words, theshaft is either rigid, malleable, or somewhat flexible. A rigid shaftcannot be bent. A malleable shaft is a shaft that can be readily bent bythe physician to a desired shape, without springing back when released,so that it will remain in that shape during the surgical procedure.Thus, the stiffness of a malleable shaft must be low enough to allow theshaft to be bent, but high enough to resist bending when the forcesassociated with a surgical procedure are applied to the shaft. Asomewhat flexible shaft will bend and spring back when released.However, the force required to bend the shaft must be substantial.

[0063] II. Helical Loop Structures

[0064] As illustrated for example in FIGS. 1-7, a catheter 10 inaccordance with a preferred embodiment of a present invention includes ahollow, flexible catheter body 12 that is preferably formed from twotubular parts, or members. The proximal member 14 is relatively long andis attached to a handle (discussed below with reference to FIGS. 8-15),while the distal member 16, which is relatively short, carries aplurality of spaced electrodes 18 or other operative elements. Theproximal member 14 is typically formed from a biocompatiblethermoplastic material, such as a Pebax® material (polyether blockemide) and stainless steel braid composite, which has good torquetransmission properties. In some implementations, an elongate guide coil(not shown) may also be provided within the proximal member 14. Thedistal member 16 is typically formed from a softer, more flexiblebiocompatible thermoplastic material such as unbraided Pebax® material,polyethylene, or polyurethane. The proximal and distal members, whichare about 5 French to about 9 French in diameter, are preferably eitherbonded together with an overlapping thermal bond or adhesively bondedtogether end to end over a sleeve in what is referred to as a “buttbond.”

[0065] At least a portion of the distal member 16 has a generallyhelical shape. The number of revolutions, length, diameter and shape ofthe helical portion will vary from application to application. Thehelical portion of the distal member 16 in the embodiment illustrated inFIGS. 1-7, which may be used to create lesions in or around thepulmonary vein, revolves around the longitudinal axis of the catheter 10one and one-half times in its relaxed state. The diameter of the helicalportion can be substantially constant over its length. The diameter may,alternatively, vary over the length of the helical portion. For example,the helical portion could have a generally frusto-conical shape wherethe diameter decreases in the distal direction.

[0066] The helical shape of the exemplary distal member 16 may beachieved through the use of a center support 20 (FIG. 2) that ispositioned inside of and passes within the length of the distal member.The center support 20 is preferably a rectangular wire formed fromresilient inert wire, such as Nickel Titanium (commercially availableunder the trade name Nitinol®) or 17-7 stainless steel wire, with aportion thereof heat set into the desired helical configuration. Thethickness of the rectangular center support 20 is preferably betweenabout 0.010 inch and about 0.015 inch. Resilient injection moldedplastic can also be used. Although other cross sectional configurationscan be used, such as a round wire, a rectangular cross section arrangedsuch that the longer edge extends in the longitudinal direction ispreferred for at least the helical portion. Such an orientation reducesthe amount of torsional force, as compared to a round wire, required tounwind the helical portion into an expanded configuration and collapsethe helical portion into a circular structure in the manner describedbelow. The preferred orientation of the center support 20 also increasesthe stiffness of the helical portion in the longitudinal direction,which allows the physician to firmly press the present structure againsttissue. The center support 20 is also preferably housed in an insulativetube 21 formed from material such as Teflon™ or polyester.

[0067] In the illustrated embodiment, the proximal end of the helicalcenter support 20 is secured to a C-shaped crimp sleeve (not shown) thatis located where the proximal and distal members 14 and 16 are bonded toone another and is mounted on a guide coil (not shown) which extendsthrough the proximal member 14 to the distal end thereof. The distal endof the guide coil is located in the area where the proximal and distalmembers 14 and 16 are bonded to one another. This bond also anchors theproximal end of the center support 20 to the distal end of the proximalmember 14. The distal end of the center support 20 is secured to a tipmember 22 which is in turn secured to the distal end of the distalmember 16 with adhesive. Additional details concerning the placement ofa center support within the distal member of a catheter can be found incommonly assigned U.S. patent application Ser. No. 09/150,833, entitled“Catheter Having Improved Torque Transmission Capability and Method ofMaking the Same,” which is incorporated herein by reference.

[0068] The exemplary catheter 10 also includes a stylet 24 that enablesthe physician to manipulate the helical portion of the distal member 16and adjust its shape from the at rest shape illustrated in FIG. 1. Forexample, the stylet 24 can be moved distally to deform the helicalportion of the distal member 16 in the manner illustrated in FIG. 3 orproximally to deform the helical portion in the manner illustrated inFIGS. 4-5 b. The physician can also rotate the stylet 24 in onedirection, which will cause the helical portion of the distal member 16to unwind and so that its diameter increases, as illustrated in FIGS. 6and 7, or rotate the stylet in the other direction to cause the distalmember to wind up and its diameter to decrease.

[0069] In any of these states, the helical portion will define an openarea interior to the electrodes 18 through which blood or other bodilyfluids can flow. As a result, the helical portion can be used to createa circumferential lesion in or around the pulmonary vein, or otherbodily orifice, without occluding fluid flow.

[0070] The stylet 24, which is preferably formed from inert wire such asNitinol® or 17-7 stainless steel wire and should be stiffer than thecenter support 20, extends through the catheter body 12 from theproximal end of the proximal member 14 to the distal end of the distalmember 16. There, it may be secured to either distal end of the centersupport 20 or to the tip member 22. The stylet 24 is located within thecatheter body 12 except in the area of the helical portion of the distalmember 16. Here, apertures 26 and 28 are provided for ingress andegress. In order to insure that the stylet 24 moves smoothly through thecatheter body 12, the stylet is located within a lubricated guide coil30 (FIG. 2) in the preferred embodiment.

[0071] The exemplary catheter 10 illustrated in FIGS. 1-7 is not asteerable catheter and, accordingly, may be advanced though aconventional steerable guide sheath 32 to the target location. Thesheath 32 should be lubricious to reduce friction during movement of thecatheter 10. With respect to materials, the proximal portion of thesheath 14 is preferably a Pebax® and stainless steel braid composite andthe distal portion is a more flexible material, such as unbraidedPebax®, for steering purposes. The sheath should also be stiffer thanthe catheter 12. Prior to advancing the catheter 10 into the sheath 32,the stylet 24 will be moved to and held in its distal most position(i.e. beyond the position illustrated in FIG. 3) in order to straightenout the helical portion of the distal member 16. The stylet 24 willremain in this position until the helical portion of the distal member16 is advanced beyond the distal end of the sheath 32. A sheathintroducer, such as those used in combination with basket catheters, maybe used when introducing the distal member 16 into the sheath 32.

[0072] As illustrated for example in FIGS. 1, 3, 4 and 6, the exemplarycatheter 10 may also include an anchor member 34 which allows thecatheter to be precisely located relative to the pulmonary vein (orother orifice). More specifically, advancing the anchor member 34 intothe pulmonary vein aligns the helical portion of the distal member 16with the pulmonary vein. The physician can then manipulate the stylet 24to bring the helical portion of the distal member 16 into the desiredconfiguration and press the distal member (and electrodes 18) firmlyagainst the region of tissue surrounding the pulmonary vein to create acircumferential lesion around the pulmonary vein. Alternatively, thephysician can advance the helical portion of the distal member 16 intothe pulmonary vein and thereafter manipulate the stylet 24 so that thehelical portion expands and brings the electrodes 18 into contact withthe interior of the pulmonary vein so that a circumferential lesion canbe created within the vein. In the illustrated embodiment, the anchormember 34 is simply the portion of the distal member 16 that is distalto the helical portion. Alternatively, a separate structure may besecured to the distal end of the distal member 16. The exemplary anchormember 34 is approximately 1 to 2 inches in length, although otherlengths may be used to suit particular applications.

[0073] The exemplary catheter 10 illustrated in FIGS. 1-7 should be usedin conjunction with a handle that allows the physician to move thestylet 24 proximally and distally relative to the catheter body 12 andalso allows the physician to rotate the stylet relative to the catheterbody. One example of such a handle, which is generally represented byreference numeral 38, is illustrated in FIGS. 8-12. The handle 38includes distal member 40, a rotatable knob 42 that is connected to thestylet 24 and a rotatable end cap 44 that is connected to the catheterbody 12 through the use of a tip member 45. Specifically, the catheterbody 12 is bonded to the tip member 45 which is in turn bonded to therotatable end cap 44. The handle also includes a transition piece 46that is used to secure the distal member 40 to a proximal member 48(FIG. 11). The proximal end of the proximal member 48 includes a port(not shown) that receives an electrical connector from a power supplyand control device. Alternatively, the distal and proximal members 40and 48 may be combined into a unitary structure having a shape that iseither the same as or is different than the illustrated shape of thecombined distal and proximal members.

[0074] Turning first to the proximal and distal actuation of the stylet24, the proximal portion of the stylet and lubricated guide coil 30extend through the catheter body 12 and into the handle 38, asillustrated in FIG. 11. The lubricated guide coil 30 is secured to aseat 50 within the distal member 40. A stylet guide 52 that includes aguide slot 54 is secured within the distal member 40. The stylet guide52 is preferably formed from a lubricious material such as acetal, whichis sold under the trade name Delrin®. The stylet 24 passed through theguide slot 54 and is anchored to a threaded spool 56 that is secured to,and is preferably integral with, the rotatable knob 42. The rotatableknob and spool are secured to the proximal member 40 with a cap screwand nut arrangement or the like that extends through aperture 57 (FIG.12). The threads on the spool 56 act as guides to control the manner inwhich the stylet 24 winds onto and unwinds from the spool. Anchoring isaccomplished in the illustrated embodiment by inserting the stylet 24into an anchoring aperture 58 and securing the stylet within theaperture with a set screw (not shown) that is inserted into a set screwaperture 60.

[0075] Proximal rotation of the knob 42 and threaded spool 56, i.e.rotation in the direction of arrow P in FIG. 9, will cause the stylet 24to move proximally and wind onto the threaded spool. As this occurs, thestylet 24 will travel within the guide slot 54 towards the knob 42 inthe direction of the arrow in FIG. 11. Distal rotation of the knob 42 onthe other hand, i.e. rotation in the direction of arrow D in FIG. 9,will cause the stylet 24 to move distally, unwind from the threadedspool 56 and travel away from the knob within the guide slot 54.

[0076] In the preferred embodiment illustrated in FIGS. 8-12, the stylet24 can be rotated relative to the catheter body 12 because the stylet isanchored with the handle distal member 40, while the catheter body issecured to the end cap 44 that is free to rotate relative to the distalmember. Referring more specifically to FIGS. 10 and 11, the rotatableend cap 44 is mounted on an end cap support member 66. A set screw (notshown) engages a longitudinally extending slot 68 formed in the supportmember 66 and holds it in place within the distal member 40. The distalportion of the support member 66 includes a circumferentially extendingslot 70. A series of set screws 72, which have a diameter that issubstantially equal to the width of the slot 70, pass through the endcap 44 into the slot. This arrangement allows the end cap 44 to rotaterelative to the support member 66 and, therefore, rotate relative to thehandle distal member 40. The proximal end of the end cap support member66 includes a relief surface 74 that prevents unnecessary stress on thestylet 24 as it travels back and forth within the guide slot 54.

[0077] To rotate the stylet 24 relative to the catheter body 12, thephysician may hold the end cap 44 in place and rotate the handle distalmember 40 relative to the end cap. When such rotation occurs, the stylet24 will rotate within the catheter body 12. The catheter body 12, on theother hand, will be held in place by virtue of its connection to the endcap 40. As a result, the stylet 24 can be used to apply torsional forcesto the helical portion of the proximal member 16 to move the helicalportion between the various states illustrated in FIGS. 1, 4, and 6.

[0078] Another handle that may be used in conjunction with the exemplarycatheter 10 is illustrated for example in FIGS. 13-15. Exemplary handle76 includes a main body 78 and a stylet control device 80 that can beused to move the stylet 24 proximally and distally and that can also beused to rotate the stylet relative to the catheter body 12. The styletcontrol device 80 consists essentially of a housing 82, a rotatablethreaded spool 84 and knob 86 arrangement, and a housing support member88 that supports the housing such that the housing may be rotatedrelative to the main body 78.

[0079] The exemplary housing 82 is composed of two housing members 90and 92 which fit together in the manner illustrated in FIG. 14. A styletguide 94, which includes a guide slot 96, is located within the housing82. The stylet guide 94 is secured in place and prevented from rotatingrelative to the housing 82 with a set screw (not shown) that restswithin a positioning slot 98 after being inserted though an aperture 100in the housing. The stylet 24 passes through the guide slot 96 and, in amanner similar to that described above with reference to FIGS. 8-12, isanchored in an anchoring aperture 102. The stylet 24 is secured withinthe anchoring aperture 102 with a set screw (not shown) that is insertedinto a set screw aperture 104. Here too, proximal rotation of the knob86 (arrow P in FIG. 13) will cause the stylet 24 to wind onto thethreaded spool 84, thereby pulling the stylet proximally, while distalrotation (arrow D in FIG. 13) will cause the stylet to unwind from thespool and move distally.

[0080] In the preferred embodiment illustrated in FIGS. 13-15, thehousing 82 includes a post 106 that may be inserted into the housingsupport member 88, which is itself fixedly secured to the handle mainbody 78. A circumferentially extending slot 108 is formed in one end ofthe post 106. In a manner similar to the end cap 44 illustrated in FIGS.8-12, the post 106 may be secured to the housing support member 88 byinserting a series of set screws 110 though a corresponding series ofsupport member apertures and into the slot 108. As described in greaterdetail below with reference to FIG. 15, the catheter body 12 is fixedlysecured to the handle main body 78. Thus, rotation of the housing 82relative to the housing support member 88 and, therefore, the main body78 will cause the stylet 24 to rotate relative to the catheter body 12.Upon such rotation, the stylet 24 will apply torsional forces to thehelical portion of the proximal member 16, thereby causing it to movebetween the states illustrated in FIGS. 1, 4, and 6.

[0081] As illustrated for example in FIG. 14, the exemplary handle mainbody 78 is a multi-part assembly consisting of handle members 112 and114, a base member 116 and a strain relief element 118. Handle member114 includes a series of fasteners 120 a-c which mate with correspondingfasteners (not shown) on the handle member 112. Handle member 114 alsoincludes a wire guide 122 which is used to centralize the electricalwires. A cutout 124 is formed at the proximal end of the handle member114 and a similar cutout (not shown) is formed in the handle member 112.The cutouts together form an opening for an electrical connector from apower supply and control device. The base member 116 includes anaperture 126 for seating the housing support member 88 and a cylindricalpost 128 on which the strain relief element 118 is fixedly mounted.

[0082] The catheter body 12 may be inserted into and bonded to the basemember 116 in the manner illustrated for example in FIG. 15. Thus, thecatheter body 12 is fixed relative to the handle 76. The guide coil 30is secured within a guide coil seat 130 and the stylet 24 extendsthrough the guide coil seat and into the housing support member 88 inthe manner shown.

[0083] Like the catheter illustrated in FIGS. 1-7, the helical catheter132 illustrated in FIG. 16 includes a catheter body 12 having a proximalmember 14 and a distal member 16 with a helical portion, a plurality ofelectrodes 18, and an anchor member 34. The catheter illustrated in FIG.16 does not, however, include a stylet 24. In order to compensate forthe decrease in manipulability associated with the lack of a stylet, thecenter support may be formed from material such as actuator-typeNitinol® (discussed in detail below) which has shape memory propertiesthat are activated at a temperature higher than body temperature. Theshape memory properties allow the physician to, for example, cause thehelical portion of the distal member 16 to expand from the stateillustrated in FIGS. 4-5 b (albeit with respect to catheter 10) to thestate illustrated in FIGS. 6 and 7 by energizing the electrodes 18.

[0084] The helical portion of the distal member 16 in the catheter 132should be flexible enough that the helical portion will deflect andstraighten out when pushed or pulled into the sheath, yet resilientenough that it will return to its helical shape when removed from thesheath. In addition, the proximal and distal end of the helical portionshould be oriented at an angle relative to the longitudinal axis of thecatheter 36 (preferably about 45 degrees) that facilitates a smoothtransition as the distal member 16 is pushed or pulled into the sheath32. Also, because the catheter 132 lacks the stylet 24, it may be usedin conjunction with any conventional catheter handle.

[0085] A guidewire may be used in conjunction with the cathetersillustrated in FIGS. 1-16 to position the sheath 32 in the mannerdescribed below with reference to FIG. 25.

[0086] Another exemplary catheter that relies on materials which haveshape memory properties activated at high temperatures is illustrated inFIGS. 16a-16 c. Exemplary catheter 133, which is a non-steerablecatheter that may be inserted into a patient over a guidewire 135,includes a catheter body 12′ having a proximal member 14′ and a distalmember 16′, a plurality of electrodes 18, and an anchor member 34. Thecatheter 133 also includes a shape memory core wire 137 that is frictionfit within the distal member 16′ and heat set into a helicalconfiguration. The core wire 137 is relatively flexible at bodytemperature. As such, a stylet 24 may be used to maintain the core wire137 and electrode supporting distal member 16′ in the linear stateillustrated in FIG. 16a.

[0087] The core wire 137 and distal member 16′ may be driven to thehelical state illustrated in FIG. 16c by heating the core wire 137.Resistive heating is the preferred method of heating the core wire 137.To that end, electrical leads 139 (only one shown) are connected to theends of the core wire 137 and supply current to the core wire. Thestylet 24 and guidewire 135 should be pulled in the proximal directionbeyond the distal member 16′ prior to heating the core wire 137.

[0088] A suitable material for the core wire 137 is a shape memory alloysuch as actuator-type Nitinol®. Such material has a transitiontemperature above body temperature (typically between about 550° C. and70° C.). When the material is heated to the transition temperature, theinternal structure of the material dynamically changes, thereby causingthe material to contract and assume its heat set shape. Additionalinformation concerning shape memory alloys is provided in T. W. Dueriget al., “Actuator and Work Production Devices,” Engineering Aspects ofShape Memory Alloys, pp. 181-194 (1990).

[0089] The exemplary catheter body 12′ is substantially similar to thecatheter body 12 described above. However, as illustrated in FIG. 16b,the exemplary catheter body 12′ includes five lumens—a central lumen 141and four outer lumens 143. The guidewire 135 passes through the centrallumen 141. The core wire 137 and conductor 139 are located within one ofthe outer lumens 143 and the stylet 24 is located in another outerlumen. The other two outer lumens 143 respectively house electrode wires168 and temperature sensor wires 174 (discussed in Section IV below). Ofcourse, other catheter body configurations, such as a three outer lumenconfiguration in which the electrode and temperature sensor wires arelocated in the same lumen, may be employed.

[0090] The exemplary catheter 133 illustrated in FIGS. 16a-16 c alsoincludes a pair of radiopaque markers 145 and 147 that may be used toproperly position the helical portion of the catheter. Morespecifically, because the core wire 137 contracts equally in the distaland proximal directions, the catheter 133 should be positioned such thatthe target tissue area is located at about the mid-point between theradiopaque markers 145 and 147 prior to actuating the core wire 137. Toform a lesion within the pulmonary vein, for example, the anchor member34 may be inserted into the pulmonary vein to such an extent that themid-point between the radiopaque markers 145 and 147 is located at thetarget site within the vein. Actuation of the core wire 137 will causethe electrode supporting distal member 16′ to assume the helical shapeillustrated in FIG. 16c and press against the vein so as to achieve asuitable level of tissue contact.

[0091] Once the lesion has been formed, the core wire 137 may bedeactivated and the stylet 24 may be moved back into the distal member16′ to return the distal member to the linear state illustrated in FIG.16a. A diagnostic catheter (not shown) may then be advanced through thecentral lumen 141 to map the vein and insure that a curative lesion hasbeen formed.

[0092] III. Other Loop Catheters

[0093] A loop catheter 134 in accordance with a preferred embodiment ofanother present invention is illustrated in FIGS. 17-21. The loopcatheter 134 includes a hollow, flexible catheter body 136 that ispreferably formed from two tubular parts, or members. The proximalmember 138 is relatively long and is attached to a handle, while thedistal member 140, which is relatively short, carries a plurality ofspaced electrodes 18 or other operative elements. The proximal member138 is typically formed from a biocompatible thermoplastic material,such as a Pebax® material (polyether block emide) and stainless steelbraid composite, which has good torque transmission properties and, insome implementations, an elongate guide coil (not shown) may also beprovided within the proximal member. The distal member 140 is typicallyformed from a softer, more flexible biocompatible thermoplastic materialsuch as unbraided Pebax® material, polyethylene, or polyurethane. Theproximal and distal members are preferably either bonded together withan overlapping thermal bond or adhesive bonded together end to end overa sleeve in what is referred to as a “butt bond.”

[0094] The distal portion of the proximal member 138 includes apre-shaped curved portion (or elbow) 142. Although other curvatures maybe used, the curved portion 142 in the illustrated embodiment is aninety degree curve with a radius of about 0.5 inch. The presetcurvature may be accomplished in a variety of manners. Preferably, thecurved portion 142 is preset through the use of a thermal formingtechnique (100° C. for 1 hour). The preset curved portion 142 in theillustrated embodiment results in a loop that is in plane with theremainder of the catheter 134. However, as discussed below withreference to FIGS. 22-24, curvatures that result in an out-of-plane loopmay also be employed.

[0095] The preset curvature may also be accomplished through the use ofa pre-shaped spring member (not shown) formed from Nitinol® or 17-7stainless steel that is positioned within the proximal member 138 andanchored where the proximal and distal members 138 and 140 are bonded toone another. Such a spring member would preferably be rectangular incross-section and have a nominal radius of about 0.5 inch. Anotheralternative would be to adjust the location of the proximalmember/distal member bond and use the center support 150 (discussedbelow) to provide the preset curvature.

[0096] The exemplary catheter 134 illustrated in FIGS. 17-21 alsoincludes a pull wire 144. The pull wire 144 is preferably a flexible,inert cable constructed from strands of metal wire material, such asNitinol® or 17-7 stainless steel, that is about 0.012 inch to about0.025 inch in diameter. Alternatively, the pull wire 144 may be formedfrom a flexible, inert stranded or molded plastic material. The pullwire 144 is also preferably round in cross-section, although othercross-sectional configurations can be used.

[0097] As illustrated for example in FIG. 18, the pull wire 144 in theexemplary embodiment extends into an opening 146 in a tip member 148 andis secured to a center support 150 with a stainless steel crimp tube152. More specifically, the pull wire 144 passes through a bore 154 inthe distal end 156 of the crimp tube 152 and abuts the center support150. The in-line connection of the center support 150 and pull wire 144allows for a reduction in the overall diameter of distal portion of thecatheter body 136. The tip member 148 is preferably formed from platinumand is fixedly engaged with, for example, silver solder, adhesive orspot welding, to the distal end 156 of crimp tube 152. The centersupport may be electrically insulated with a thin walled polyester heatshrink tube 158 that extends beyond the proximal end of the crimp tube152. The pull wire 144 extends proximally from the tip member 148 andpreferably back into the catheter body 136 through an aperture 158 tothe proximal end of the catheter body. Alternatively, the pull wire cansimply be run proximally within the interior of the sheath 32 along theexterior of the catheter body 136. Other pull wire configurations, othermethods of attaching the pull wire to the catheter body, and methods ofreducing stress on the pull wire are disclosed in aforementioned U.S.application Ser. No. 08/960,902.

[0098] The center support 150 is similar to the center support 20illustrated in FIG. 2 in that it is positioned inside the distal member140 and is preferably a rectangular wire formed from resilient inertwire, such as Nitinol® or 17-7 stainless steel wire. The thickness ofthe rectangular center support 150 is preferably between about 0.010inch and about 0.020 inch. Resilient injection molded plastic can alsobe used. Although other cross sectional configurations can be used, suchas a round wire, a rectangular cross section arranged such that thelonger edge extends in the longitudinal direction is preferred. Thisorientation reduces the amount of force required to pull the distalmember 140 into the loop configuration illustrated in FIG. 17. Thepreferred orientation also increases the stiffness of the loop in thelongitudinal direction, which allows the physician to firmly press thepresent structure against tissue. The center support 150, which may alsobe heat set into the preset curvature, is secured within the catheterbody 136 in the manner described above with reference to FIGS. 1-7.

[0099] As illustrated for example in FIG. 19, the curved portion 142 ofthe proximal member 138 will be straightened out when the catheter 134is within the sheath 32. After the exemplary catheter 134 has beendeployed, the curved portion will return to its curved state and thepull wire may be retracted to form the loop illustrated in FIG. 17.

[0100] The loop in the embodiment illustrated in FIGS. 17-21 is in planewith the remainder of the catheter body 136. A stylet 160 allows thephysician to reorient the loop from the orientation illustrated in FIG.17 to, for example, the orientation illustrated in FIGS. 20 and 21 whichis ninety degrees out of plane. The stylet 160 is soldered to the tipmember 148 and extends through the sheath 32 to the proximal endthereof. The tip member 148 is, in turn, bonded to the distal member140. The stylet 160 is preferably formed from inert wire such asNitinol® or 17-7 stainless steel wire and should be stiffer than thecenter support 150.

[0101] The combination of the pre-shaped curved portion 142 and thestylet 160 advantageously allows the physician to precisely position theloop relative to the pulmonary vein or other bodily orifice. As aresult, the exemplary catheter 134 can be used to create lesions in oraround the pulmonary vein or other bodily orifice in an expedient mannerwithout occluding blood or other bodily fluid flow.

[0102] Another exemplary loop catheter, which is generally representedby reference numeral 162, is illustrated in FIGS. 22-24. The loopcatheter illustrated in FIGS. 22-24 is substantially similar to the loopcatheter illustrated in FIGS. 17-21 and common elements are representedby common reference numerals. Here, however, there is no stylet. Loopcatheter 162 also includes a pre-shaped curved portion 164 thatpositions the loop out of plane with respect to the remainder of thecatheter. More specifically, the exemplary pre-curved portion 164positions the loop ninety degrees out of plane with respect to theremainder of the catheter 162 and orients the loop such that the opening166 defined thereby faces in the distal direction. Other curvatures maybe used as applications require.

[0103] A sheath 32 and a guidewire 161 (FIG. 25), as well as thecurvature of the pre-shaped curved portion 164, allows the physician toprecisely position the loop relative to the pulmonary vein or otherbodily orifice. As a result, the exemplary catheter 162 may be used toexpediently create lesions in or around the pulmonary vein or otherbodily orifice without the occlusion of blood or other bodily fluids.

[0104] The exemplary loop catheter 162 illustrated in FIGS. 22-24 has agenerally circular loop (note FIG. 24). However, other loopconfigurations, such as the elliptical loop configuration on thecatheter 167 illustrated in FIG. 26, may be employed as applicationsrequire.

[0105] Still another exemplary loop catheter, which is generallyrepresented by reference numeral 163, is illustrated in FIGS. 27 and 28.The loop catheter illustrated in FIGS. 27 and 28 is substantiallysimilar to the loop catheter illustrated in FIGS. 17-21 and commonelements are represented by common reference numerals. Here, however,the pull wire 144 extends along the exterior of the proximal member 138and the stylet 160 is secured to a collar 165 that is free to slidealong the distal member 140 when the distal member is in thesubstantially linear state illustrated in FIG. 27. The collar 165, whichhas an inner diameter that is slightly larger than the outer diameter ofthe distal member 140, is preferably formed from a relative softmaterial, such a soft plastic or silicone rubber. Mechanicalinterference will cause the collar 165 to become fixed in place when thedistal member 140 is bent. As a result, the physician can move thecollar 165 to the desired location on the distal member 140 prior toformation of the loop to vary the location at which pushing and pullingforces will be applied by the stylet 160 and, therefore, vary theultimate shape and orientation of the loop.

[0106] The exemplary loop catheter 163 illustrated in FIGS. 27 and 28has a generally circular loop. However, other loop configurations, suchas the elliptical loop configuration on the catheter 167 illustrated inFIG. 26, may be employed as applications require.

[0107] The catheters illustrated in FIGS. 17-28 may be used inconjunction with conventional catheter handles that provide for themanipulation of one or more control elements, such as a pull wire and astylet. Suitable handles are disclosed in U.S. Pat. Nos. 5,871,523 and5,928,191.

[0108] IV. Electrodes, Temperature Sensing and Power Control

[0109] In each of the preferred embodiments, the operative elements area plurality of spaced electrodes 18. However, other operative elements,such as lumens for chemical ablation, laser arrays, ultrasonictransducers, microwave electrodes, and ohmically heated hot wires, andsuch devices may be substituted for the electrodes. Additionally,although electrodes and temperature sensors are discussed below in thecontext of the exemplary catheter probe illustrated in FIGS. 1-7, thediscussion is applicable to all of the probes disclosed herein.

[0110] The spaced electrodes 18 are preferably in the form of wound,spiral coils. The coils are made of electrically conducting material,like copper alloy, platinum, or stainless steel, or compositions such asdrawn-filled tubing (e.g. a copper core with a platinum jacket). Theelectrically conducting material of the coils can be further coated withplatinum-iridium or gold to improve its conduction properties andbiocompatibility. A preferred coil electrode is disclosed in U.S. Pat.No. 5,797,905. The electrodes 18 are electrically coupled to individualwires 168 (see, for example, FIG. 2) to conduct coagulating energy tothem. The wires are passed in conventional fashion through a lumenextending through the associated catheter body into a PC board in thecatheter handle, where they are electrically coupled to a connector thatis received in a port on the handle. The connector plugs into a sourceof RF coagulation energy.

[0111] As an alternative, the electrodes may be in the form of solidrings of conductive material, like platinum, or can comprise aconductive material, like platinum-iridium or gold, coated upon thedevice using conventional coating techniques or an ion beam assisteddeposition (IBAD) process. For better adherence, an undercoating ofnickel or titanium can be applied. The electrodes can also be in theform of helical ribbons. The electrodes can also be formed with aconductive ink compound that is pad printed onto a non-conductivetubular body. A preferred conductive ink compound is a silver-basedflexible adhesive conductive ink (polyurethane binder), however othermetal-based adhesive conductive inks such as platinum-based, gold-based,copper-based, etc., may also be used to form electrodes. Such inks aremore flexible than epoxy-based inks.

[0112] The flexible electrodes 18 are preferably about 4 mm to about 20mm in length. In the preferred embodiment, the electrodes are 12.5 mm inlength with 1 mm to 3 mm spacing, which will result in the creation ofcontinuous lesion patterns in tissue when coagulation energy is appliedsimultaneously to adjacent electrodes. For rigid electrodes, the lengthof the each electrode can vary from about 2 mm to about 10 mm. Usingmultiple rigid electrodes longer than about 10 mm each adversely effectsthe overall flexibility of the device, while electrodes having lengthsof less than about 2 mm do not consistently form the desired continuouslesion patterns.

[0113] The portion of the electrodes that are not intended to contacttissue (and be exposed to the blood pool) may be masked through avariety of techniques with a material that is preferably electricallyand thermally insulating. This prevents the transmission of coagulationenergy directly into the blood pool and directs the energy directlytoward and into the tissue. For example, a layer of UV adhesive (oranother adhesive) may be painted on preselected portions of theelectrodes to insulate the portions of the electrodes not intended tocontact tissue. Deposition techniques may also be implemented toposition a conductive surface only on those portions of the assemblyintended to contact tissue. Alternatively, a coating may be formed bydipping the electrodes in PTFE material.

[0114] The electrodes may be operated in a uni-polar mode, in which thesoft tissue coagulation energy emitted by the electrodes is returnedthrough an indifferent patch electrode (not shown) externally attachedto the skin of the patient. Alternatively, the electrodes may beoperated in a bi-polar mode, in which energy emitted by one or moreelectrodes is returned through other electrodes. The amount of powerrequired to coagulate tissue ranges from 5 to 150 w.

[0115] As illustrated for example in FIGS. 5a and 5 b, a plurality oftemperature sensors 170, such as thermocouples or thermistors, may belocated on, under, abutting the longitudinal end edges of, or inbetween, the electrodes 18. Preferably, the temperature sensors 170 arelocated at the longitudinal edges of the electrodes 18 on the distallyfacing side of the helical (or other loop) structure. In someembodiments, a reference thermocouple 172 may also be provided. Fortemperature control purposes, signals from the temperature sensors aretransmitted to the source of coagulation energy by way of wires 174(FIG. 2) that are also connected to the aforementioned PC board in thecatheter handle. Suitable temperature sensors and controllers whichcontrol power to electrodes based on a sensed temperature are disclosedin U.S. Pat. Nos. 5,456,682, 5,582,609 and 5,755,715.

[0116] As illustrated for example in FIGS. 5a and 5 b, the temperaturesensors 170 are preferably located within a linear channel 171 that isformed in the distal member 16. The linear channel 171 insures that thetemperature sensors will directly face the tissue and be arranged inlinear fashion. The illustrated arrangement results in more accuratetemperature readings which, in turn, results in better temperaturecontrol. As such, the actual tissue temperature will more accuratelycorrespond to the temperature set by the physician on the power controldevice, thereby providing the physician with better control of thelesion creation process and reducing the likelihood that embolicmaterials will be formed. Such a channel may be employed in conjunctionwith any of the electrode (or other operative element) supportingstructures disclosed herein.

[0117] Finally, the electrodes 18 and temperature sensors 172 caninclude a porous material coating, which transmits coagulation energythrough an electrified ionic medium. For example, as disclosed in U.S.application Ser. No. 08/879,343, filed Jun. 20, 1997, entitled “SurfaceCoatings For Catheters, Direct Contacting Diagnostic and TherapeuticDevices,” electrodes and temperature sensors may be coated withregenerated cellulose, hydrogel or plastic having electricallyconductive components. With respect to regenerated cellulose, thecoating acts as a mechanical barrier between the surgical devicecomponents, such as electrodes, preventing ingress of blood cells,infectious agents, such as viruses and bacteria, and large biologicalmolecules such as proteins, while providing electrical contact to thehuman body. The regenerated cellulose coating also acts as abiocompatible barrier between the device components and the human body,whereby the components can now be made from materials that are somewhattoxic (such as silver or copper).

[0118] Although the present inventions have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. It is intended that the scope of the presentinventions extend to all such modifications and/or additions and thatthe scope of the present inventions is limited solely by the claims setforth below.

We claim:
 1. A probe, comprising: an elongate body defining a distalregion, a proximal region, a proximal end, a curved portion having apre-set curvature and a longitudinal axis; a control element defining adistal portion associated with the distal region of the elongate bodyand extending outwardly therefrom and proximally to the proximal end ofthe elongate body; and at least one operative element supported on thedistal region.
 2. A probe as claimed in claim 1, wherein the elongatebody comprises a catheter body.
 3. A probe as claimed in claim 1,wherein the curved portion is located within the proximal region.
 4. Aprobe as claimed in claim 1, wherein the proximal region includes aproximal member defining a first stiffness, the distal region includes adistal member defining a second stiffness, and the second stiffness isless than the first stiffness.
 5. A probe as claimed in claim 1, whereinthe at least one operative element comprises a plurality of electrodes.6. A probe as claimed in claim 1, wherein the elongate body defines acontrol element aperture and the control element extends from the distalregion of the elongate body and into the control element aperture.
 7. Aprobe as claimed in claim 1, wherein the curved portion of the elongatebody defines an approximately ninety degree curvature.
 8. A probe asclaimed in claim 1, wherein the control element comprises a firstcontrol element, the probe further comprising: a second control elementsecured to a portion of the distal region of the elongate body andextending proximally therefrom.
 9. A probe as claimed in claim 8,wherein the first control element defines a first stiffness, the secondcontrol element defines a second stiffness, and the first stiffness isless than the second stiffness.
 10. A probe as claimed in claim 8,wherein the distal region defines a middle area and the second controlelement is secured to the middle area.
 11. A probe as claimed in claim1, wherein the curved portion of the elongate body defines a curvedportion plane, the distal region comprises a loop defining a loop plane,and the loop plane is arranged at a non-zero angle to the curved portionplane.
 12. A probe as claimed in claim 11, wherein the loop plane issubstantially perpendicular to the curved portion plane.
 13. A probe,comprising: an elongate body defining a distal region and a proximalregion, at least a portion of the distal region having a substantiallylinear channel; and at least one temperature sensor located in thesubstantially linear channel.
 14. A probe as claimed in claim 13,wherein the at least one temperature sensor comprises a plurality ofaxially spaced temperature sensors.
 15. A probe as claimed in claim 13,further comprising: at least one operative element carried on the distalregion of the elongate body.
 16. A probe as claimed in claim 15, whereinthe at least one operative element comprises an electrode.
 17. A probeas claimed in claim 13, wherein the elongate body defines a longitudinalaxis and the substantially linear channel is substantially c-shaped in across-section perpendicular to the longitudinal axis.
 18. A probe,comprising: an elongate body defining a distal region, a proximalregion, a proximal end, a distal end and a longitudinal axis; a firstcontrol element defining a distal portion associated with the distalregion of the elongate body and extending outwardly from the distal endand proximally to the proximal end of the elongate body; a secondcontrol element extending proximally to the proximal end of the elongatebody, the second control element being movably secured to the distalregion of the elongate body; and at least one operative elementsupported on the distal region.
 19. A probe as claimed in claim 18,wherein the second control element includes a collar slidably mounted onthe distal region of the elongate body.
 20. A probe as claimed in claim19, wherein the collar is relatively soft.
 21. A probe as claimed inclaim 19, wherein the collar and distal region of the elongate body arerespectively constructed and arranged such that the collar will bemovable relative to the distal region when the distal region is in asubstantially linear state and the collar will be substantially fixedrelative to the distal region when the distal region is in a curvedstate.
 22. A probe as claimed in claim 18, wherein the elongate bodyincludes a curved portion having a preset curvature.